Tape measures have been used for many years to accurately measure distances between two points and the lengths of objects. Tape measures typically include a housing having an opening through which a measuring tape is drawn. The measuring tape has indicia printed thereon that are used to measure distances. When measuring a distance, the measuring tape is unwound from a storage spool as it is drawn through the opening of the housing. When the measuring task is complete, the measuring tape is rewound onto the storage spool.
In recent years, electronic tape measures have been developed which electronically track the length of a measuring tape unwound from a storage spool. Electronic tape measures typically include a reading element in communication with the storage spool that generates electric pulses corresponding to the length of the measuring tape drawn from the spool. The electric pulses are counted by operational circuitry, which converts the pulses into a digital readout provided on a visual display.
One electronic tape measure is disclosed in U.S. Pat. No. 5,142,793 to Crane which teaches a housing, a reel located within the housing and a measuring tape wound on the reel. The measuring tape is extendable through an opening in the housing as the reel is unwound. A first measuring element is associated with the reel for generating incremental measuring data and a second measuring element generates absolute measuring data as the measuring tape is extended. A processor responsive to both the incremental measuring data and the absolute measuring data generates an output that reflects the linear extension of the measuring tape from the housing. The device also includes a visual display for showing information related to the linear extension of the measuring tape.
U.S. Pat. No. 5,426,863 to Biggel discloses a combination tape measure and calculator. The tape measure includes a measuring tape having equally spaced holes along the length thereof. The holes are read by closely spaced optical readers arranged to generate incremental unit signals that are transmitted to a microprocessor mounted in a case.
U.S. Pat. No. 5,433,014 to Falk et al. discloses a digital tape measure including a transmitter for transmitting measurements to a remote location. The tape measure includes a housing, a measuring tape having a series of optical markings, an optical sensor for sensing the optical markings when the tape is extended or retracted, a logic circuit in communication with the optical sensor for providing a digital signal representative of the length of the tape drawn from the housing, and a transmitter connected to the logic circuit for transmitting the digital signal to the remote location. A receiving unit is provided at the remote location for receiving, storing and displaying the measurements.
U.S. Pat. No. 5,286,972 to Falk et al. discloses a photoelectric measuring device with a digital display. The measuring device measures distance by optically scanning the length of a line as it is unwound from a reel. The line is provided with a plurality of dye marks placed at spaced intervals. The dye marks are detected by an optical sensor in communication with a circuit that maintains a count indicative of the length of the line. The count is displayed on an LED display.
The above-described devices generally use measuring tapes having a substantial width and thickness that limits the length of tape, such as 100 meters or less, that can be conveniently stored on a single spool. Tape measures having distances of over one hundred meters are rare because longer tapes will substantially increase the overall size of the tape measure housing, thereby making the tape measure extremely bulky and burdensome to operate.
Another problem with conventional tape measures relates to maintenance and replacement costs. Tape measures are frequently damaged because they are used in harsh environments resulting in the measuring tape being damaged. A damaged measuring tape cannot accurately measure a distance or cannot be rewound onto a storage spool. As a result, the measuring tape must be repaired or replaced at substantial cost. In many instances, a brand new tape measure must be purchased.
Another problem relates to the accuracy of electronic tape measures. Many conventional electronic tape measures are inaccurate or unreliable because they don't account for the hanging radius of the measuring tape on the storage spool as the tape is unwound from the storage spool.
Thus, there is a need for an electronic tape measure that enables users to measure longer distances. There is also a need for a durable electronic tape measure, which allows the measuring element extended from a housing to be easily replaced, at low cost. There is also a need for an electronic tape measure that is accurate and reliable.